PSI - Issue 70

Blessy Grant C J et al. / Procedia Structural Integrity 70 (2025) 247–254

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1. Introduction Joint failures are common in earthquakes, especially in buildings where Beam-column joints are critical components for transferring loads between horizontal beams and vertical column. The Northridge earthquake with its magnitude 6.7 was an impactful seismic event that hit the San Fernando Valley region of Los Angeles, California, on January 17, 1994. One of the notable aspects of the destruction as an aftereffect of the Northridge earthquake was the prevalence of beam-column joint failures in buildings throughout the affected area. These failures occurred primarily in structures with weak beam-strong column configuration, where the ground floor lacks adequate lateral support. The Northridge earthquake highlighted the vulnerability of such buildings to seismic forces, particularly due to inadequate or poorly designed beam-column connections. The 1995 great Hanshin Earthquake hit the southernmost part of Hyogo Prefecture in Japan on January 17, 1995. It has its magnitude of 6.9 causing widespread devastation. It resulted in approximately 6434 fatalities. The Bhuj earthquake of 2001 was a devastating seismic event that occurred on January 26, 2001. It occurred due to tectonic activity along the Indian and Eurasian tectonic plates. The earthquake had a magnitude of 7.7. These materials perform poorly under lateral seismic forces because they are brittle and cannot flex or deform to absorb energy. Common issues included poor reinforcement detailing and lack of ductility, which led to catastrophic collapses. Many multi-storey buildings in urban areas had soft stories which are prone to collapse under lateral seismic loads. Insufficient reinforcement like lack of proper shear reinforcement, lack of proper design in beam column joints to dissipate energy effectively, and the lack of stiffness in these floors led to massive destruction. Structures in earthquake-prone areas must be designed to allow for controlled deformation without collapsing. The 2015 Nepal earthquake, also known as the Gorkha earthquake, struck Nepal on April 25, 2015, having its magnitude 7.8. Earthquake damage often leads to a reduction in the stiffness and strength of a structure. This deterioration is used to guide repair decisions for partially damaged structures where damage may not be immediately apparent. Damage can be estimated by assessing the decrease in structural stiffness, provided there is a reliable correlation between damage and stiffness degradation. The advantages of Laced Reinforced Concrete (LRC) elements have been detailed in the comprehensive manual TM 5 – 1300. Key advantages include greater rotational capacity at supports, strain hardening that extends beyond the yield plateau, minimized spalling once the yield limit is reached, and robust shear resistance. Parameswaran et al. (1986) conducted extensive and thorough experimental investigations on LRC elements with cold-worked deformed bars. Based on the findings, they confidently recommended 4° as the ideal value for support rotation in LRC elements for blast-resistant construction. This indicates a failure deflection of around 1/25 to 1/30 of the span on a simply supported beam. Keshava Rao et al. (1992) conducted an experiment to understand the behavior of laced reinforced concrete (LRC) structural elements under blast loading. Their study aimed to assess whether ductility observed in monotonic tests could be replicated under blast loading conditions and to determine if a 25% strength increase, as recommended by design guidelines could be effectively applied and to investigate the yield patterns developed in different structural elements under extreme loading conditions. Consequently, a handbook on the design of LRC for blast-resistant structures (STEC Pamphlet No. 21, 1996) was produced as a result of the investigation. They concluded that LRC structures possess superior blast resistance compared to conventional RC structures. The used of LRC techniques improved the performance in terms of both ductility and strength, making it a promising approach for designing blast resistant structures. Srinivasa Rao (1996) observed the behavior of Laced Reinforced Concrete Beams related to ductility characteristics by testing about 20 specimens under monotonic and cyclic loading conditions. When the Shear – span depth ratio is lesser than 2.5, the ductile failure in Reinforced Concrete (RC) beams with conventional stirrups is not achievable. The LRC beams even with significant tension steel were capable of eliminating its brittle failure has been concluded from the test results. The test results indicated that LRC beams, even those with significant tension steel, are capable of eliminating brittle failure. This ensures high level of ductility and maintains resistance across an extended yield plateau. Lakshmanan et al. (2008) conducted a study to explore the performance of reinforced concrete beams that were reinforced with steel fibers and laced for shear loading. The researchers also conducted reversed cyclic shear loading tests over the Laced Concrete Beams, incorporating with steel fibers and without fibers. The findings indicated that